About 15% of American households get their drinking water from private wells. If the well goes dry or the water becomes contaminated it could impact both your health and the value of your home. Generally speaking, private wells consist of a pump, well casing (a pipe to prevent collapse of the well hole), a well head and a well cap to protect the well. The well casing is a solid pipe until the saturated zone then slotted or perforated within the saturate zone so that the pump can draw from the groundwater the slotting serves to filter out sand and silt. The groundwater that is pumped by the well is not a massive underground river or lake, but simply saturated earth.
Groundwater is water that fills the cracks and pores of rocks and sediments that lie beneath the surface of the earth saturating those materials. Gravel, sand, sandstone, or fractured rock have large connected spaces that allows water to flow through them allowing an aquifer to form. Impervious layers of clay and bedrock prevent ground water moving from one space to another. Usable aquifers are bound by impermeable layers; however, if the groundwater is isolated and prevented from flowing the groundwater is said to be perched and is unusable.
Groundwater is ubiquitous and like all water on earth it comes from precipitation that percolates through the soil until it reaches the zone of saturation. Though groundwater is everywhere the quantity and usability of groundwater varies from location to location based on geology and precipitation. Due to its protected location underground, most groundwater is naturally clean and free from pollution. Not understanding the nature of groundwater we have abused it. In the past when we buried things in the earth, fuel tanks, industrial and household waste at landfills, poured solvents out into the dirt, used excessive amounts of fertilizer, had uncontrolled waste from animal feedlots we were contributing to the contamination of groundwater. Homeowner disposal of chemicals, treating a home for termites, excessive use of fertilizers (even organic), and malfunctioning septic systems can all impact onsite groundwater quality and potentially down gradient sites.